Optimizing post-transplantation cell therapies to enhance graft-versus-leukemia effects in hematological malignancies

Allogeneic hematopoietic cell transplantation (HCT) can cure patients with high-risk hematologic malignancies. Donor T and natural killer (NK) cells contribute to graft-versus-leukemia (GVL) effects that provide relapse protection. Post-HCT relapses often represent inadequate GVL, but alloreactive lymphocytes that confer GVL may also cause graft-versus-host-disease (GVHD). Here, we review recent developments to selectively augment GVL while minimizing GVHD. Insights into the unique mechanisms of post-HCT T cell dysfunction highlight interventions to enhance GVL-mediating T cells. Early clinical data suggest that adoptive transfer of engineered donor T cells, expressing either transgenic T cell receptors specific for minor histocompatibility antigens presented exclusively on recipient hematopoietic cells or chimeric antigen receptors binding surface proteins on malignant cells, can mitigate post-HCT relapse. NK cells, key GVL mediators after haploidentical HCT, can be induced into a highly functional memory-like state and administered to HCT recipients to enhance GVL. These innovations promise much-needed improvements in post-HCT outcomes.